On Sat, Dec 23, 2023 at 1:51 AM Tejun Heo <tj@xxxxxxxxxx> wrote:
>
> Hello,
>
> On Fri, Dec 22, 2023 at 11:31:01AM +0000, Yafang Shao wrote:
> > Introducing a new kfunc: bpf_cpumask_set_from_pid. This function serves the
> > purpose of retrieving the cpumask associated with a specific PID. Its
> > utility is particularly evident within container environments. For
> > instance, it allows for extracting the cpuset of a container using the
> > init task within it.
> >
> > Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> ...
> > +__bpf_kfunc bool bpf_cpumask_set_from_pid(struct cpumask *cpumask, u32 pid)
> > +{
> > + struct task_struct *task;
> > +
> > + if (!cpumask)
> > + return false;
> > +
> > + task = get_pid_task(find_vpid(pid), PIDTYPE_PID);
> > + if (!task)
> > + return false;
> > +
> > + cpumask_copy(cpumask, task->cpus_ptr);
> > + put_task_struct(task);
> > + return true;
> > +}
>
> This seems awfully specific. Why is this necessary? Shouldn't the BPF prog
> get the task and bpf_cpumask_copy() its ->cpus_ptr instead?
Good point. I missed the bpf_cpumask_copy(). Will use it instead.
--
Regards
Yafang
